Managing MEA hydration cycling life

a technology of mea hydration and cycling life, applied in the field of electrochemical conversion cells, can solve the problems of significant degradation of the mechanical durability of mea, and achieve the effect of prolonging the life of membrane fatigue and minimizing membrane stress

Active Publication Date: 2011-01-04
GM GLOBAL TECH OPERATIONS LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006]The present inventor has recognized that membrane stress can be minimized by properly controlling variables like membrane dehydration rate, water content, temperature, and heating / cooling rate. By minimizing membrane stress, the membrane fatigue life can be prolonged. According to one aspect of the present invention, a fatigue life contour map is created based on a suitable S-N curve and a suitable membrane stress model or some other suitable means for calculating membrane stresses for a given dehydration rate, water content, temperature, and starting water content when dehydration takes place. It is contemplated that suitable S-N curves should correspond closely to the membrane at issue and may be determined experimentally or approximated based on available membrane data.

Problems solved by technology

One of the consequences of the aforementioned hydration cycling is significant degradation of the mechanical durability of the MEA.

Method used

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  • Managing MEA hydration cycling life
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Examples

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Embodiment Construction

[0019]The details of the present invention can be illustrated in further detail by referring to the particular fatigue life contour map illustrated in FIG. 2 and taking, as an example, a particular application that requires the need to decrease the water content of the proton exchange membrane from a relatively wet condition, λ=23.7, to a dryer condition of λ=4, at a temperature of about 80° C. For comparative purposes, the fatigue life cycle for dehydration along path A at a substantially constant rate of about 0.25 H2O / H+ per second would result in a fatigue life of about 6000-7000 cycles. According to the methodology of the present invention, referring to dehydration along path B, the membrane is initially dehydrated at a rate of about H2O / H+ per second until the membrane hydration λ reaches a value where the expected fatigue life would fall below an acceptable level, e.g., 13000, until the targeted water content λ=4 is reached. In this embodiment of the present invention, the ex...

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Abstract

In accordance with one embodiment of the present invention, a method of operating an electrochemical conversion cell is provided wherein the method comprises the steps of (i) initiating a membrane dehydration sequence when the membrane is characterized by an initial membrane hydration λWET and (ii) maintaining the membrane dehydration sequence until the membrane is characterized by a target membrane hydration λDRY. According to the method, the membrane dehydration sequence is characterized by a drying rate that varies in a manner that substantially corresponds to a fatigue life contour map of the membrane. Additional methods and corresponding systems are contemplated.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application Ser. No. 11 / 467,596 is related to U.S. patent application Ser. Nos. 11 / 695,270, filed Apr. 2, 2007; 11 / 464,226, filed Aug. 14, 2006; and 11 / 466,832, filed Aug. 24, 2006.BACKGROUND OF THE INVENTION[0002]The present invention relates to electrochemical conversion cells, commonly referred to as fuel cells, which produce electrical energy by processing first and second reactants. For example, electrical energy can be generated in a fuel cell through the reduction of an oxygen-containing gas and the oxidation of a hydrogenous gas. By way of illustration and not limitation, a typical cell comprises a membrane electrode assembly (MEA) positioned between a pair of flowfields accommodating respective ones of the reactants. More specifically, a cathode flowfield plate and an anode flowfield plate can be positioned on opposite sides of the MEA. The voltage provided by a single cell unit is typically too small for useful appli...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): H01M8/04
CPCH01M8/04156H01M8/04223H01M8/04298H01M8/04529H01M8/04731H01M8/04753H01M8/04835H01M2008/1095Y02E60/50H01M8/04225H01M8/04228H01M8/04302H01M8/04303
InventorLAI, YEH-HUNG
OwnerGM GLOBAL TECH OPERATIONS LLC